1. Field
The following description relates to a near-field radio frequency identification (RFID) reader antenna, and more particularly, to a near-field RFID reader antenna for separately recognizing adjacent items to which a plurality of small RFID tags are attached, such as wines displayed on a shelf in a store or chip trays on a casino table, using its near field.
2. Description of the Related Art
Application of RFID is expanding from pallet or box tagging to item-level tagging. In general, high frequency (HF)-band RFID technology has been preferred for item-level tagging, but has problems including tag size and price, reading distance, data processing speed, compatibility with an existing ultra high frequency (UHF)-band RFID standard, and so on.
While the HF-band RFID technology uses a magnetic field coupling mechanism, UHF-band RFID technology uses backscattering of electromagnetic waves. The UHF-band RFID technology shows a reading distance of about 3 to 5 m, which is longer than that of the HF-band RFID technology, and thus has been widely used for physical distribution, material management, etc., in units of pallets or boxes.
However, in the application field of separately recognizing a large amount of densely aggregated items, the read ratio of the UHF-band RFID technology abruptly deteriorates due to scattering and interference of electromagnetic waves. To overcome this drawback of the UHF-band RFID technology in separately recognizing items, research on RFID technology using a UHF-band near field is actively under way.
When the UHF-band near field is used, the magnetic field coupling mechanism or an electric field coupling mechanism is selected according to an item to which a tag is attached and a service environment, and a large amount of items can be separately recognized, unlike the HF-band RFID technology using the magnetic field coupling mechanism.
However, according to the UHF-band near-field RFID technology, a reader antenna must be designed with a different concept from conventional far-field REID technology. In other words, each item recognition environment, a tag position, distribution of a near-field, etc., must be considered in designing the reader antenna.
Also, in order to separately recognize and manage a variety of items densely aggregated is on a display stand such as a shelf using the near-field RFID technology, a near-field must cover the entire display stand to remove a fading zone. Thus, the reader antenna needs to be designed such that an electric field and magnetic field are formed in several directions.